Below is the best post I read about this Eps. I copied it from comments on RC from Junk. (Spoiler tag because it is a long post.)

Spoiler:

Ano Hana is a lovely series. Easily among the loveliest Iíve seen. It feels as if itís been created with much tenderness and care.

I appreciate that there hasnít been any sitcom-style character development. Iíll be a bit disappointed if Menmaís mom suddenly accepts the other kids or if everybody with unrequited feelings suddenly gains new outlooks on their futures and can casually walk away from what has become years of emotional investments. What I do hope to see is new resolutions to move in better directions even if hurt and disappointment still lingers. The pain of losing someone to death never goes away and we all fill the holes left behind with our most precious and extreme feelings. What the characters in this series need is a way to start learning how to live with what happened, not major changes. Or, at least, thatís my opinion. Iím not trying to say a differing view is wrong, just sharing a different viewpoint in that the series has value in how it has operated more like messy, unresolved real life as opposed to a tight plot. At not point while watching did I feel it was lazy, sloppy, or poorly plotted/written. Again, just an opinion.

If I remember correctly, Jintan ran out on his mom as she prepared to die and, at this point, Iím assuming he never went back. Menma did and the conversation she had with his mom seems to be the reason Menma wanted to do something for Jintan. Did Menma want the group to do something to see his mom off to heaven so she can be properly reincarnated? Fireworks, maybe? Iím guessing that whatever Jintanís mom asked of or told to Menma is what she wanted when Menma asked them all to meet that day. It seems that it is connected to whatever Menmaís ghostly wish is. Clearly there is a connection; how many times have we seen Menma paying respects at his momís shrine? Maybe Menma feels a need to help Jintan get over his Mom and his witnessing of her going to heaven might help him realize his mom experienced that, too. And that itís not bad.

On another topic, I think itís become clear Poppo saw Menmaís death. From what was said, it seems he ran off after her (or possibly her and Jintan, his exact motives are still unclear: naive, optimistic boy wanting to heal the group rifts, chasing a crush, or wanting to hit Jintan for what he said? or all?.
Possibly 2 things happened: he saw her accident but was unable to prevent it, thus has been carrying a terrible memory as he could only watch Menma die and/or he startled her and accidently triggered her fall which, again, he witnessed and has had to carry a secret guilt. It would help explain why his behavior towards Menma has been quite different from the others and possibly also why heís the only one who really went out into the world and appears to have changed in those years. He saw the truth so hasnít had the mystery of what happened hanging over him, plus he might have seen how easily death can come even to the young. If he has dwelled on what happened, he hasnít let it stop his personal development, it may have driven him as the others got stuck in confusion and wondering.

Iím unconvinced he felt romantically towards Menma as kids; considering the type of boy he was I imagine he would have been thrilled to have the attention of any of the girls. I suspect the seeming emergence of his feelings for Menma is complicated: youthful affection which grows distorted by grief and imagination. But the way he chanted at Jintan here seems to be the beginning of Poppoís anger for what Jintan said about Menma surfacing. Thatís not necessarily proof of youthful romantic feelings for one girl; it could be a loyal, idealistic boyís idea of how girls (in general) should be treated, particularly by someone as admired as Jintan.